Virologic, biochemical, physiologic, and electron microscopic methods will be used to study the effects of picornaviruses on nerve-muscle interactions in vitro. The study is centering on (1) the effect of neuronal infection on the development of neurites and the formation of neuromuscular junctions; (2) the effect of neuronal infection on the morphology and contractile properties of muscle; and (3) the effect of muscle infection on the morphology, physiology, and metabolism of connecting neurons. In addition, factors which influence the susceptibility to, and the outcome of, viral infection of neuron-muscle cultures will be studied. Such factors as the influence of putative spinal cord neurotransmitters, pharmacologic blockage, and physiologic stimulation will be examined in relation to various aspects of viral replication.